1. Field of the Invention
The present invention relates to equipments used in the electrical treatment and monitoring of human bodies. More specifically, the present invention relates to a defibrillator using impedance-compensated defibrillation pulses to apply treatment by contact with the surface of a patient's skin, which is most conveniently accessible to the rescuer.
2. Description of the Related Art
Sudden cardiac arrest is often caused by ventricular fibrillation (VF) in which abnormal and very fast electrical activity occurs in the heart. During VF, the heart cannot pump blood effectively as it causes the individual muscle fibers within the heart to contract in an unsynchronized way. In treating victims of cardiac arrest with a defibrillator, it is important that the treatment be performed very rapidly as their chances of surviving the cardiac arrest decrease drastically over time following the cardiac arrest. Studies have shown that defibrillation shocks delivered within one minute after VF achieve up to 100% survival rate. However, the survival rate falls to approximately 30% if 6 minutes elapse before the defibrillation shock is delivered. Beyond 12 minutes, the survival rate is almost zero. Therefore, a quick response to cardiac arrest in administering a defibrillation shock at the rescue scene is critical.
Medical equipment manufacturers have developed Automated Electronic Defibrillators (AEDs) to provide early defibrillation. AEDs deliver a high-amplitude current pulse, waveform, or shock to the heart in order to restore the patient's heart rhythm to a normal level. AEDs are widely deployed in both medical and non-medical settings, including private residences, public buildings, public transportation vehicles, airplanes, businesses, etc. AEDs are equipped with a pair of electrodes to deliver a series of shocks to a patient as needed. An electrode may include a conductive foil layer that resides upon a conductive adhesive layer, a lead wire electrically connected to the conductive foil layer to the AED, and an insulation layer for covering the conductive foil layer. The adhesive layer serves to physically and electrically displace the conductive foil layer to a patient's skin. Electrodes tend to deteriorate in time; thus, it is necessary to know their operating condition when they are used in a life-threatening situation. To this end, AEDs rely on a release liner with multiple openings to determine whether the electrodes are in a proper operating condition. When manufacturing electrodes, new electrodes are detachably mounted on a release liner in a package. Prior to use, an impedance is measured through the release layer disposed between a pair of electrodes; if the measurement is higher than the threshold impedance, the electrode is considered to be damaged, deteriorated, unfit for use.
FIG. 1 depicts the conventional AED 10 being applied to a cardiac arrest victim 2 by a rescuer 4. As shown in FIG. 1, a pair of defibrillation electrodes 12 and is placed on anterior-anterior (AA) positions on the victim's torso. The rescuer selects different sizes of electrodes 12 for defibrillating adults and children. A main drawback of the conventional AED 10 is that it requires time-consuming steps in the deployment and use of a defibrillator. First, the placement of electrodes 12 necessitates removing clothes from an unconscious patient 2, sometimes requiring the use of a scissor 8 or knife in order to gain access to the desired location on the torso of the patient 2. Removing clothes causes a longer delay for the patient 2 in waiting for the defibrillating shock. In a highly stressful emergency situation, inexperienced or infrequent operators of the AED 10 are often reluctant or do not aggressively destroy the clothing on an unconscious stranger to expose the recommended attachment areas, and further slow the rescue attempt. In addition, some victims of cardiac arrest require removal of chest hair with a razor 6 to gain access to the attachment areas, which further delays the life-saving shock treatment, thus delaying and reducing the chances of a successful rescue attempt. Moreover, even after gaining access to and attaching the defibrillation electrodes 12 by the trained rescuers of the AED 10, the delivery of the defibrillation shock often fails because the rescuers inadvertently fail to apply the electrode pads correctly, thus missing the heart. The placement of the electrodes is then repeated, which is undesirable in the course of administering the defibrillating shock
Accordingly, there is a need for an improved defibrillator that is easy to use and that enables a minimally trained user to easily, rapidly, and effectively deploy the defibrillator to treat the patient, with no or minimal clothing and hair removal.